Process of preparing silicon-zirconium alloys of reduced silicon content



Patented July 7, 1925.

UNITED STATES PATENT OFFICE.

ALEXANDER L. FEILD. OF JACK-SON HEIGHTS. NEW YORK, ASSIGNOR TO ELECTRO- METALLURGICAL COMPANY, A CORPORATION OF WEST VIRGINIA.

PROCESS OF PREPARING SILICON-ZIRCONIUM ALLOYS 0F REDUCED SILICON CO'NTENT.

N 0 Drawing.

To (7 ae/zom it may concern:

lie it known that I, ALuxANnun L. Fuim, a citizen of the United States, residing at Jackson lleights, in the county of Queens and State of New York, have invented certain-new and useful Improvements in Processes ot' Preparing Silicon-Zirconium Alloys ol' Reduced Silicon Content, of which the following is a specification.

The. invention is a process of preparing silicon-zirconium alloys of reduced siliconcontent. Typical alloys of the class contemplated are those in which a low carbon content is obtained by incorporating into the alloy a percentage of silicon which exceeds the zirconium percentage.

United States Patent 1,425,572, issued on Aug. 15, 1922 to Frederick M. Becket, describes a method whereby alloys of this class may be produced, it being understood that a low carbon content is desirable when the alloy is to be used for certain purposes, for example for addition to molten steel.

\Vhen the Becket alloy is to be added to steels the silicon content of which is already at or near the permissible limit, the

high silicon content of the alloy is 0bjec-.

tionable, since too much silicon accompanies the zirconium into the steel bath. It is the object of the present invention to reduce the silicon content of such alloys as those described in the Becket patent, and preferably to reduce the silicon percentage until it falls below the zirconium percentage, without destroying any of the advantageous characteristics of the alloy.

This object is accomplished by treating the alloy with an alkaline solvent for silicon, such as a solution of a hydroxid or carbonate of an alkali metal or a hydroxid of an alkaline-earth metal.

The process can be carried out under a wide range of conditions, including the nature of the alkali, the concentration of its solution, the proportion of alkali to alloy treated, the fineness of division of the alloy, the temperature during treatment, the composition of the alloy treated, and so forth.

Sodium hydroxid is a cheap alkali, and may be used with excellent results. Ten to thirty per cent solutions are convenient, but both higher and lower concentrations may be used. A fifty per cent excess of alkali over that theoretically necessary to react Application filed April 21, 1924. Serial No. 708,030.

with the silicon which it is found possible to remove is mentioned by way of example. lVhen the alloy is tinely powdered, as to pass a 100-mesh screen, before the alkali treatment, the removal of the. silicon is expedited, but such a fine subdivision of the alloy is by no means indispensable. Indeed it has been found that under some conditions the process can be successfully applied to alloy which has only been crushed to lumps, since these disintegrate under the action of the silcon-extracting reagent. The process may be carried out at any usual temperature. As in other chemical reactions of the same general class, it is found that stronger solutions of alkali, larger excesses of alkali, finer division of the alloy treated, and higher temperatures, expedite the silicon removal.

The following examples will illustrate the process:

I. An alloy containing 43.9% Si, 35.14% Zr, and about 16% Fe, was suitably treated with a 20% solution of NaOH. The resulting product contained only 37.9% Si and 14.17% Zr.

II. One hundred grams of an alloy containing Si 47.60%, Zr 43.52%, and Fe 5.99%, was ground to pass a 100 mesh screen and slowly added to a 30% solution of caustic soda containing about g. NaOH. The alloy was left in the caustic solution held at 90 C. for one-half hour after the final addition. Twenty-one and a. half grams of the alloy dissolved, including 0.2 grams of zirconium. The undissolved alloy contained 55.13% Zr, 34.60% Si, and 5.74"!) I Fe. The ratio of silicon to zirconium was thus reduced from 1.09 to 0.63.

Alloys such as those described in the Becket patent usually contain considerable quantities of iron, though the iron content can be reduced by appropriate measures. I have found that a low iron content facilitates the removal of silicon by the described method. It is my present belief that the optimum iron content for a maximum removal of silicon by the hereindescribed process may be determined by the following computation: If the weight of zirconium in a charge of the original alloy is multiplied by 0.6 and the product subtracted from the weight of silicon in the charge, then the weight of iron present should not materially exceed one-third of the differences so obtained. 1

The iron remains with the insoluble material after the alkali treatment. ,Where the -final product is to be added to a Steel bath, a content of metallic iron is of course immaterial. If desired, the iron can he removed completely or in part, as by leaching with a reagent such as dilute sulphuric acid which attacks the iron preferentially.

Under favorable conditions it is possible to remove so much silicon from alloys of the kind referred to that the percentage of silicon in the product obtained does not materially exceed six-tenths of the zirconium percentage.

I claim:

1. Process which comprises reducing a zirconium compound with a carbonaceous 2. Process according to claim 1 wherein the iron content of the original alloy is kept low, substantially as described.

In testimony whereof, I aflix my signature.

ALEXANDER L. FEILD. 

